On my 53 flatbed we used the 'body' tag/plate number located at the driver's door pilar. Since we had no paper work at all and since the body tag number didn't come up in the DMV data base my local police ok'ed using that number. Try to speak with a State or local police officer, my city officer was a big help. Also I found a person that works with car lots to handle all their DMV BS. For a small fee this person took care of all the DMV leg work, I'd still be standing in line.
Without the factory body tag most DMV/State Police can install a NEW tag/number, you'll just have to prove ownership via a bill of sale etc.
